Electric heating unit



May 20, 1924. 1,494,940

C. C. ABBOTT ELECTRIC HEATING UNIT Filed (kit. 17, [922 Im/entoF: Chaics C. Abbott,

yW M H is Att c nn e Patented May 20, 1924.

I UNITED SQIA-TES,

came s c. ABBOTT, or

rITTSFI'EmJ, MASSACHUSETTS, ASSIGNOB' To GENERAL mncmc COMPANY,COBPQBATION: OF NEW YORK.

nLncTmc HEATING UNIT.

Application filed October 1%, am. serm'm. 595,192.

To all whom it mag ceman:

Be it known that I, CHARLES C. ABBOTT,

a citizen of the United States, 'residin at- Pittsfield, in the countyof Berkshire, tate of Massachusetts, have'invented certain new anduseful Improvements in Electric Heating Units, of which the following isa specification.

My invention relates to electric heating units particularly to sheathwire heating unit s,.and has for its object the provision of simple,reliable and 'efiicient means for supporting the terminals thereof,

More specifically my invention relates to 1 improvements in sheath wireheating units of the helical core type, disclosed in my filed October 5,1921, of which this application is a continuation inpart. In heat- 2 ingunits of this typethe resistance conof granular insulating materialenclosed in a metallic containing sheath. To the ends of the resistancegonductor are secured terminals which project from the sheath. In. theconstruction of the heating unit, the resistance conductor with theterminals attached is first temporarily secured centrally in thesheath,.for example, bysecuring the outer ends of the terminals. Thesheath is then filled with granular insulating material and swaged tocompact the insulatin material. I have found that it is advlsable' thatmeansbe provided for positively centering the inner ends of theterminals in the sheath during the construction of the unit, otherwisethe terminals and resistance conductor may be displaced and grounded onthe sheath.

In carrying out my invention, I provide insulating members on the innerends of the terminals for holding theinner ends of the terminalscentrally of the sheath.- In one form of my invention these insulatingmembers are shaped as washers, while in a modified formof my inventionthe insulating members are square.

For a better understanding of my invention reference should be had tothe accompanying drawing in which Fig. 1 isg, a view partially insection of an assembled heating unit embodying my invention before theswaging operation; ljig. 2 is a view partially in section. showmg'acomsuch bedded a helical resistance conductor 13' pleted heating unitembodying" my inven- Fig. 3 1s a sectional 'view similar to tion; Fig 1showing-amodified form of my inventlon; while Fig...4='is a sectionalview in the direction of the arrows. Referring to Figs. 1 and 2 of thedraw ng, m one form'of my invention the heatmg unit 10 comprises ametallic cylindrica containing sheath 11 which is filled with a suitablegranular insulating material 12, as magnesium oxide, inwhich is im--taken along'the line 4'-4 of Fig. 3, looking having a terminal 14secured to eachend. The inner end of each terminal 14 is pro-.

v vided with a threadedportion 15 on which copending application, SerialNo. 505,588,.

is securedthe resistance conductor 13 and also aninsulating spacingmember 16 made of a suitable insulating material, such as mical. In theassembly'of the heating unit, duc'tor is imbedded in a compacted mass aspacing member 16, shown in the form of a washer, is screwed on thethreaded portion 15 of each terminal, and the terminals then secured tothe ends of the helical resistance conductor by screwing their threadedends into the convolutions of the resistance conductor as described andclaimed in my copendin application, Serial No. 549,636, filed pril 4,1922. Preferably the terminals are screwed into the turns of theresistance conductor until the latter engages the spacing washers.

The resistance conductor 13 with the ter minals 14 attached is theninserted in the sheath 11, the resistance conductor stretched toseparate its turns, and the terminals secured against the longitudinalpull of the resistance conductor by means of washers 17, only one ofwhich is shown, placed on the terminals and seated in the ends of the'sheath, which ends are counterbored to receive them, and a suitable clip18 secured on each terminal so as to bear against the correspondingwasher 17. One of the washers 17, for example the left-hand one, asshown,-is in the form of a star washer. The insulating spacing washers16 on the inner ends of the terminal fit loosely in the sheath 11 andserve the, purpose of holding the inner ends of the terminalssubstantially central in the sheath, the

outer ends of the terminals being centered in the sheath by the washer17. i

'In the next step in the construction of-the i unit the granularinsulating material .ings' inthe star washer 17, the s he d 12 is filledin the sheath 11 through the, openeath being in a vertical positionwithv the star washer uppermost and vibrated so as to shake theinsulating material -dbwn past the spacing .washers 16, which fit thesheath loosely enough to permit the insulating material to pass, andbetween the turns of the tends to'compact. the insulating material.After the sheath has been filled with the powdered insulating materialitis closed by means of a solid washer 17', which is inserted in thesheath'over the star ,washera'nd clip 18, and the ends of the sheathbent or pinched over at intervals 19 so asto secure the Washers at eachendin place. The heating unit has now been assembled as shown in Fig. 1.r .M'The granular insulating material 12 1s next compacted to a harddense mass by reducingtlrwdiamet'epotii sheath by sv vaging, after whichthe ends of the sheath are cut off to efi'ect the removal of the washers17 and 17 and expose the ends of terminals 14, and connecting lugs 20 ofa suitable material, such as brass, secured to .the terminals. Theseconnecting lugs may be secured as described and claimed in my aforesaidcopending application, Serial No.549,636 by providing nicks 21 in theouter ends of the terminals, inserting the nicked ends in suitablerecesses in\ the lugs 20 and then compressing the material of the lugslaterally into the nicks. Insulating washers 22 may be placed overthe'ends of the'sheath against which central in the sheath vby thespacing washer 16 during both the filling and swagingmpera-tions. As aresult the powdered insulating material 12 is distributed and com acteduniformly around the terminals where y the The spacing block 16 is ofsuch size that its corners engage with the inner surface of the sheath11, as shown in Fig. 4. Ample 7 space is thus provided around the flatsides of the blocks for the insulating material to befilled past theblocks into all parts of the sheath. The method of manufacture of thisunderstood with reference to the description ofFlgs. 1 and 2. During theswaging operation the lava'block may cru nble and become a part of thegiahular insulating material.

ductor are thus effectively centered in the .sheath so that theinsulating material is compacted uniformly around them.

i It will be observed that by means of the square spacing members theinner ends of Y Iing members shown in Figs. 1 and 2, since the roundspacing members must be sufli- "resistance conductor. This vibrationalso modified form ofmy invention will be The terminals and resistancecon- 39 ciently loose to permit the granular insulat- .90

ing material to be filled past them into the sheath. I .have found thatlava. is a material which is particularly adaptedfor the spacingmembers. Spacing members made of lava do not have the tendency to breakup 01" flake oif during the vibration of the unit when insulatingmaterial is being filled in, which tendency is characteristic of themica spacing members.

- While'I have described my invention as 10 embodied in concrete formand as operating in aspecific manner in accordance with the provislonsof the patent statutes, it should be understood that I do not limit myinvention thereto, since various modifications 1 thereof will suggestthemselves to those skilled in the art without. departing from thespirit of my invention, the scope of which is set forth in the annexedclaims.

What I claim as new and desire to secure byLetters Patent of the UnitedStates, is 1. An electric heating unit comprising a sheath, compactedgranular insulating material in said sheath, a resistance conductorterminals are thoroughly insulated fromthe embedded and supported insaid insulat- 7 terminal by providing a flattened portion 23 intheterminal near the threaded portion 15. The spaci block is seatedagainst the shoulders 23 formed by this flattened] poring material, aterminal for saidresistance conductor embedded and supported in saidinsulating material, and an insulating member for centering saidterminal in said sheath while the insulating material is put 190 in andcompacted to secure said terminal.

2. An electric heating unit comprising a heath, compacted insulatingimaterial in said sheath, a resistance conductor embedded in saidinsulating material, terminals for said resistance conductor embedded insaid insulating material projecting from the ends of said sheath, andinsulating spacing members on the inner ends of said terminals forholding the resistance conductor and terminals central of said sheathwhile the insulating material is put in and compacted to secure them.

3. An electric heating unit comprising a sheath, granular insulatingmaterial in said sheath compacted by swaging to a hard and dense mass, aresistance conductor embedded in said insulating material, terminals forsaid resistance conductor embedded in said insulating material, andinsulating spacing members'on the inner ends of'said terminals forholding the resistance conductor and terminals central of said sheathwhile the insulating material is put in and compacted by swaging thesheathwhereby the resistance conductor and terminals are secured. I

4. An electric heating, unit comprising a. sheath, compacted granularinsulating materialin said sheath, a resistance conductorembedded insa'id insulating material, terminals. for said 'resistance conductorembedded in said insulating material, and insulating spacing members onthe inner ends of said terminals for holding the resistance conductorand terminals central of the sheath while the insulating material is putin and compacted, said spacing members being adapted to permit 'saidinsulating ma terialbeing filled into said sheath.

5. An electric heating unit comprising a cylindrical sheath,compacted-granular insulating material in saidsheath, a resistanceconductor embedded in said insulating material, terminals for saidresistance conductor embedded in said insulating material, andnon-circular insulating spacing members-0n the inner ends of saidterminals for holding the resistance conductor and the inner ends ofsaid terminals central while the insulating-material is put in thesheath and compacted.

6. An electric heating unit comprising a cylindrical sheath, com actedgranular insulating material in sai sheath, a resistance conductorembedded and supported in said insulating material, terminals for saidresistance conductorembedded and supported in said insulating material,and insulating spacing members on the inner ends of said terminals forholding the resistance conductor and terminals central of the sheathwhile the insulating material is put in and compacted, said spacingmembers being provided with flat sides past which said insulatingmaterial may be filled into said sheath.

7. An electric heating unit comprising a sheath, compacted granularinsulating material in said sheath, a resistance-conductor embedded insaid insulating material, terminals for 7 said' resistance conductorembedded in said .insulating material, and square insulating spacingmembers secured to the inner ends of said terminals for holding theresistance conductor and terminals central of the sheath while thesheath is being filled with the insulating material and swaged tocompact it.

8. An electric heating unit comprising a sheath, compacted granularinsulating material in said sheath, a helical resistance conductorembedded in said insulating material, terminals for said resistanceconductor embedded in said insulating material having threaded portionson which the ends of said resistance conductor are screwed so as to besecured thereto, flattened portions forming shoulders on said terminalsadjacent said threaded portions, and insulating s acing members securedon said terminals etween said shoulders and the ends of said resistanceconductor for holding the resistance conductor and terminals central ofthe sheath while the insulating material is put in and compacted wherebythe resistance conductor and terminals are secured.

'In witness whereof, I have hereunto set my hand this 13th dayofOctober, 1922.

CHARLES E, ABBOTT.

